The oscillating piston/rotating cylinder engine has been described in P. E. Morgan, U.S. Pat. No. 3,516,392. In this type of engine, an annular cylinder is rotated in a predetermined ratio to the oscillations of a plurality of pairs of oscillating pistons contained within the cylinder. The pistons are oscillated so that adjacent pistons in each pair are moved alternately toward and away from each other for the respective strokes of a four-stroke cycle internal combustion engine. Intake ports, exhaust ports, and ignition means in the rotating cylinder are located by the rotation of the cylinder with respect to the pistons in accordance with the firing order and cycle of the engine. While the Morgan engine is capable of favorable efficiencies as compared with those of conventional reciprocating piston engines, increasingly rigid standards of fuel economy and emissions control have made further improvements in mechanical and thermal efficiency highly desirable. In this regard, for example, the Morgan engine has a relatively large number of moving parts that add weight and complexity, and create friction losses, while the design of the pistons (essentially disc-shaped, with flat sides) does not optimize the extraction of useful energy from combustion during the power stroke.
It would be highly desirable, therefore, to improve the Morgan engine, whereby the advantages of the basic oscillating piston/rotating cylinder design are retained, while increasing efficiency by reducing the number of moving parts and optimizing piston design.